Getting married at a young age won't make you poor.Having kids at a young age will make you poor for sure.
I don't know about your country,but rising a kid from it's birth to the age of 18 costs more than 150,000 USD in the USA.The cost might be lower in the other countries,but it's still a significant amount of money.
I agree getting married early does not mean that you will be poor, the fact that you have another person protecting your back and they have you too to protect theirs is great but adding kids to the mix will surely make you poor since in the economy of today you need a lot of preparation to get to the highest paid jobs, something that is very difficult if you have to feed a big family.
I'm not so sure about that number. $150,000 is $8,333 per year. That would be $694 per month. Where the heck is all that money going for one kid? I'm 100% sure that poor people in the US don't spend that much on their kids. I studied in the US and I could like on that easily each month, not counting my studies. When you have more kids, you spend less per child. You have hand-me-downs and it's cheaper per person to cook for more people. I don't live in the US right now, but there are 2 people in my family and we usually spend less than that on 2 adults. Everything is possible if you believe.
There are frugal people that spend less than that per child and that is fine and in fact I have seen higher numbers than the ones published here but it does not matter, adding a kid when you are very young is going to make very difficult for you to become successful in the future, in the economy of today you need a lot of time and effort to get a good job and if you have a child you will need to concentrate on getting money now and not on improving yourself and your ability to make money in the future.